A microscope is known from U.S. Pat. No. 4,737,022 in which laser light is coupled into the reflected light beam path for conventional illumination. However, the laser light does not per se serve for illumination of the object. On the contrary, an autofocus signal is produced by means of the laser light. The lasers are therefore designed to have a very low power, so that their radiation does not act harmfully on the eyes.
Laser scanning units adaptable to conventional microscopes using a laser beam for object illumination are known from U.S. Pat. No. 5,032,720 and WO 92/02839. These microscopes differ from the present invention in that the coupling-in of the laser beam takes place from above, in the photo outlet of the microscope. Coupling-in the laser beam from above has two disadvantages. First, such a system results in a very high, potentially unstable structure. Secondly, in such a system, the photo outlet is no longer available for conventional applications.
The second disadvantage is avoided in the laser scanning microscope of the present inventor's assignee (described, for example, in the brochure No. 42-920 d with the printer's imprint AW-H-VII/88 Uoo). In this microscope, the laser is arranged vertically behind the microscope stand. The laser beam is coupled into the microscope via a beam path running above (parallel to) the conventional reflected light illumination beam path. The coupling-in takes place via a fully reflecting mirror, arranged in a slide. One slide position is unoccupied, and in this switching position the observation light reaches the photo outlet. In this system, the disadvantage lies in the construction of the whole laser scanning unit being adapted to a special stand, especially in regards to the height of the stand. Consequently, an adaptation of the laser illuminator to different stands is only possible by a structural modification.
A laser scanning microscope that couples the laser beam into the microscope via the conventional reflected light illumination beam path is known from the article "Laser Scanning Microscope--Construction and Applications" in GIT Fachz. Lab. 28, (1984). To prevent eye damage, the visual observation beam path is blocked during laser scanning operation. The article does not specify by what means the visual observation beam path is blocked. Nor does it specify whether or how a possible operating error (that results in the observation beam path being freed, in spite of the laser scanning operation) is prevented from arising.
A microscope with a laser micromanipulator is known from European Patent 0,101,572-B1. The manipulation beam is coupled into the microscope via the conventional reflected light illumination beam path. A shutter is arranged between the laser and the illuminating reflector. However, its mode of operation is not described in more detail. The illuminating reflector is constructed as a partially reflecting mirror. The laser light scattered or reflected at the object is always reflected into the ocular by the illuminating reflector. When looking into the ocular and focusing on strongly reflecting object structures, considerable danger of eye damage exists for the observer.